What is coil on plug?
Coil on plug (COP) gives you a separate ignition coil for each cylinder. Instead of a single ignition coil, ignition distributor and spark plug wires, there is an individual ignition coil for each cylinder.
What are the advantages of COP?
Stronger Spark
With the single coil ignition system originally equipped to 850’s and 1998 x70’s, spark has to travel from the ignition coil, through the a wire, to the ignition rotor, ignition cap, to another spark wire and finally to the spark plug. Each one of these paths and junctions present resistance to the spark, thus decreasing its’ strength and also adding a wear component that must be replaced. With COP the ignition coil is located directly on top of the spark plug, increasing power at the spark plug gap. This allows for a wider spark gap, which in turns equals faster, more even combustion and higher engine power output.
Increased Dwell at High RPM
A major problem of using a single coil to fire 5 cylinders, is that the amount of time the coil has to charge is limited. An ignition coil has to be charged for a specific amount of time to generate the most amount of spark energy. This charge time is called ignition or spark dwell. An undercharged ignition coil will reduce spark power. At high engine speeds a single coil firing 5 spark plugs can’t fully charge, as the coil must start charging to fire the next cylinder. With the stock ignition system, past 5100RPM the coil can no charge to full capacity. This means that the spark energy is decreasing right when you need it the most! With an individual ignition coil for each cylinder there is no limitation and the dwell time can be kept at optimal levels throughout the RPM range.
More Accurate Spark Timing
The single coil system’s reliance on a spinning rotor and cap to distribute the spark has latency built in. This latency isn’t drastic, usually equal to .5° or less of ignition advance, but it can cause enough of problem at high loads to cause mild knock/pre-detonation.
Smoother Running
By switching to COP you’ll notice a much smoother engine idle and off idle response. The difference can be drastic.
Use Any Ignition Coil
With an individual spark trigger for each cylinder you can use any type of ignition coil you want. ME7 coils are recommended, due to their ease of installation, but you can use any ignition coil that triggers from a 5V logic signal. For example, LS2 coils could be used, which provide an incredibly strong spark and many in the world of high horsepower forced induction have had great success with these coils.
Resistorless Plugs
Standard spark plugs use an internal resistive element to block electromagnetic interference (EMI ). Without this resistive element, EMI will propagate through spark plug wires, which act as antennae. This EMI can wreak havoc on your engine’s sensor signals and cause rough running or static in your car stereo. Although this resistive element is required to quell EMI, it has the unwanted side effect of decreasing spark power. By using COP, spark plug wires are eliminated and therefore resistor less plugs can be used, thus increasing your spark power to an even greater level!
How you can get COP
If you’re looking to make the switch to COP, we offer 3 options;
You can add COP to a full tune. Simply select ‘Coil On Plug’ from the add-ons menu. The COP add one comes with a plug and play, brand new sub-loom for the coils which connects to the ECU via an external, high quality Deutsch connector. Optionally, for a OEM+ look, you can elect to integrate COP wiring directly into the factory loom and re-pin the ECU connector for the additional wires.
If you’re looking to tune the car yourself, or just want to run a stock R tune with COP, you can add the option to a tune it yourself ECU.
If you’re comfortable soldering small components and want to handle everything yourself, you can purchase instructions on how to modify the ECU yourself. This also comes with a factory tune modified for COP.
For any option above, you will need to source your own coils. It is not recommend to install used coils, as they most likely won’t be up to task of providing spark at elevated power levels. We recommend genuine Bosch coils, part 0221604008. In our experience no factory replacement brand provides as much spark power or offers the same longevity as Bosch. If you have used coils, which you believe to be in good condition, remove the spark plug tube well boot and inspect the back of the coil. Small cracks from the top of the coil are usually OK, but cracks behind the boot indicate a worn coil which isn’t suitable for higher than stock level power.
